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I need to know how many FPS it takes to go 0-60 at 6.7 seconds

  1. Nov 11, 2008 #1
    Hello everyone.
    I got a speeding ticket for doing 53mph in a 35mph zone. (he origionally said 55mph so both calculations would be great) I was at a dead stop he said I punched it and got to 55mph before he pulled me over. My truck is a 2007 tundra that goes 0-60 in 6.7 seconds and the quarter mile time is 13.924seconds @ 98.800MPH. I am going this weekend to measure how many feet it took him to pull me over. My plan is to show the judge there is no possible way I accelerated that fast. This is a $280 ticket so please help me. Thank you so much.
  2. jcsd
  3. Nov 11, 2008 #2


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    53 mph is 77.7 fps.
    Assuming constant acceleration, you'd accelerate at 60/6.7=8.96 mph/s.
    So 53 mph would take 53/8.96=5.9s.
    With the acceleration constant, the average speed is 77.7fps/2=38.9 fps
    And the distance is 38.9*5.9=229 feet
  4. Nov 11, 2008 #3


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    So how fast *were* you going when you saw the red and blue lights behind you?
  5. Nov 11, 2008 #4
    I had a similar incident a couple years ago when a guy took the front end off my car. I used conservation of momentum and my tire tracks to show that the guy was speeding when he hit me. Long story short, the judge didn't care that I could prove my innocence and since I am a young white male the system automatically finds me guilty regardless of any evidence.

    Good luck in court but unless you can call an expert witness, such as a licensed professional engineer your pretty much SOL.
  6. Nov 12, 2008 #5
    Thank you Russ Watters!!! That is exactly what I needed there is no possible way he got me going that fast. I pulled over is a shorter distance :)

    And Berkeman I looked when I saw the lights and I was going about 40 still a little over but not what he got me doing.
  7. Nov 12, 2008 #6


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    Somewhat related incident:

    The brother of a friend of mine got caught speeding, where the cop used a radar gun to determine his speed.

    He went to court, and argued that he was travelling on a road that was at an angle with respect to where the police officer was. That is, he was not going directly towards or away from the officer. He got the cop to agree that, in that situation, the radar gun would give the wrong reading.

    What the officer failed to realize was, he had to be going even faster than what the radar gun indicated, so he was definitely speeding nonetheless!
  8. Nov 12, 2008 #7
    (1) how can you prove where you were when his radar gun said 53 mph?

    (2) In some states, there is no real difference between exceeding the limit by 1 mph or by 18 mph. So, it may not really matter if you were going 36 or 53. And if the judge thinks you are wasting his time, he can fine you like you were going 53.

    (3) russ watters calc is nice, but it does assume constant acceleration. How are you going to prove that your acceleration was constant?

    Finally, you just admitted to us you were exceeding the limit by about 5 mph. Pay your fine like a man.
  9. Nov 16, 2008 #8
    My experience has been that judges are rarely swayed by the physics but will listen your argument to see if you can raise a reasonable doubt as to the circumstances. A plea of guilty to a lesser speed during that argument will help.

    3) This can work both ways. The initial acceleration is higher for street vehicles, meaning that you will reach a higher speed in a shorter time than if the acceleration was constant. However, you also will require more distance to get to a specific speed. Can you measure the distance from the stop to where the speed reading was taken and post that?
  10. Nov 16, 2008 #9


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    I'm assuming radar wasn't used because it's clear the cop got the speed wrong. What most likely happened, is that you started accelerating sooner and/or faster than the cop, and the cop sped up to 55mph in order to reclose the gap, not realising that he was gaining on you at the time, or the cop assumed that you slowed down when what actually happened was he was just gaining on you and that you were never going 55mph.

    The issue here is if the cop is willing to admit he made a mistake, which is unlikely. Then it's up to the judge to determine believablity.

    I don't know where you got this ticket in, but in the USA, most speeds between 25mph (shool zones), and the maximum (65mph to 80mph depending on the state) follow the safe speed law. Regardless of the posted speed, it's possible that going faster is still safe depending on the conditions (little or no traffic), and tickets have been fought and won in this case. An extreme example, was a judge determined it was safe to go 100mph on a remote Montana highway (before Montana had speed limits for highways). This isn't likely to help in this case unless you get the judge to agree that you were going around 40mph in a 35mph zone.

    Anyway, even though you're technically innocent, it's unlikely you'll prevail in court, unless you get an attorney. It doesn't seem fair, but the technical aspect of this is that attorneys can't knowingly allow defendants to commit perjury, so your statements become more "believable" if you have an attorney.
  11. Nov 16, 2008 #10


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    Good point. At least air resistance makes this true, and there may be other factors, depending on transmission gearing and speeds/shifts.

    I like Jeff's practical legal comments as well.
  12. Nov 16, 2008 #11
    As you noted, the gear ratios and also the torque converter (I'm assuming an automatic) will give a much higher initial acceleration rate, which is why you can spin the tires at low speed but not at high speed.

    I didn't have an attorney and lost. They may not be related though; the other "witness" lied through his teeth and the judge believed him. He told his story with more conviction than I did. I was not as good as the court appointed attorney either.
  13. Dec 16, 2008 #12
    I was at a light and the cop was directly behind me. He used no radar no laser and when I asked if I could see proof he said that he had none.... His argument is 100% flawed.

    I was at the light the light turned green i accelerated and next thing I know his lights were on. I actually would be better off if I had the total feet covered it takes my car to get to 53 and 55.
  14. Dec 16, 2008 #13

    Ranger Mike

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    A one who is NOT a role model of safe and responsible driving, take some advise from one who has paid $ 1000's to various attorneys, Dept. of Motor Vehicle, Bail Bondsmen and Traffic court Bailiffs.....Pay the fine.

    Driving is not a Right..it is a Privledge. If , in the opinion of the law enforcement office, you operated your vehicle in an unsafe manner..GUILTY..

    I don't like it but it is the system. You can get a speeding ticket going 45 mph in a 65 MPH speed zone if conditions are not , again in the opinion of the policeman, safe.

    I like a good fight as any one but these days, unlike days of old, you young guys can't get away with diddly..

    Besides, Judges are not the most talented lawyers in any town..ifin they were , they would stick with private practice and stay wit the big dollars..in my opinion, the less talented go for public office ( a.k.a. - the last refuge for scoundrels)
  15. Dec 16, 2008 #14
    It'll be right around 200 feet, just slightly less than Russ' calculation.
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